MAY 23, 2012
This retrospective study found that incorporating corneal biomechanics into surgical planning could optimize the effect of ICRS implantation in keratoconic eyes. However, visual outcome predictions for the medium to long term are not so precise.
The authors used Ocular Response Analyzer measurements to evaluate biomechanical changes occurring in keratoconic corneas after ICRS implantation during a six-month follow-up. They reviewed the charts of 45 eyes with early, moderate or advanced keratoconus implanted with the KeraRing.
The authors found a reduction in the mean sphere and cylinder during the initial postoperative period, but these changes did not reach statistical significance. This trend of ICRS to reduce manifest sphere and cylinder supports the previous findings of other authors also using KeraRing segments. The authors write that the absence of statistical significance in refractive changes in the current series could be explained by the large preoperative and postoperative variability in refractive parameters.
At one-month postop no significant changes in corneal hysteresis (CH) or corneal resistance factor (CRF) were observed. However, significant changes in these parameters later were detected at three months and six months. Preoperative corneal biomechanical parameters were significantly correlated with postoperative corneal higher-order aberrations at all visits, although these correlations became stronger at the end of the follow-up.
Multiple regression analysis found that mean keratometry and the preoperative difference between CH and CRF were predictive of CDVA at one month postop.
The authors conclude that the modeling effect of the ring segments may be limited by biomechanical changes occurring in the postoperative medium term. The use of UVA–collagen cross-linking could be considered as an additional advisable tool to maintain the modeling effect achieved.